Q: Can you have only one imessage account on one mac even though you have multiple users?

Get them their own Apple ID to use.

Apple ID – Create

Hi,

You may also need this depending on who ends up with the current ID.

https://selfsolve.apple.com/deregister-imessage

9:23 pm      Thursday; March 31, 2016

You would also have to sign out of the Messages App by opening it and signing out.

Have you considered setting up separate User Accounts on the Mac and using it that way:

OS X Mavericks: Set up users on your Mac

OS X Mavericks: About users, administrators, groups, and guests

Cheers,

GB

Hi,

Having an email name or even an ID based on it is one thing.

It is how they are separated from your own or possibly the main Apple ID.

My Apple ID is based on  an email from way back when I had a dial-up account and first started to use these boards.

I also have several Apple ID based on trial @mac.com (which were free to try and would work for iChat as valid AIM Screen Names after that)

I resisted until iCloud about linking it to anything else.

At the point I linked it to iCloud I got an @me.com  email as well which is some places acts as if it separate and in others shows me the same info.

i.e I can log in to https://www.icloud.com/ with either name using the same password.

In Mail both that @me.com, and the later @icloud.com ID I was given, are linked to the same account in Mail and on the iCloud server I can see mail addresed to either.

In Messages the IDs work separately.

But...

If you have linked them as additional emails in the Mac or iPhone  Receive At and Send and Receive respectively then there is no longer any separation.

Also at one point I had two iPhones and used the Original Apple ID on my Mac and one iPhone and then the @me.com ID on the other iPhone only along with it's Number.

Now my Mac wanted to know if I wanted to link the Second iPhone's Number into the set up for the Mac.

At the time it seemed reasonable so I agreed to one of the Pop ups.

What that did was then link the Apple ID (@me.com) to all the devices using the Original ID.  This takes some work to remove and still 3 years later it occasionally pops up wanted to be added back.

Eric was suggesting that they have completely separate Apple IDs

It will need an outside emails for verification and Recovery purposes but don't use something that is known to be time limited such as a School/College Email.

Gail has suggested some links about setting up Separate Mac User Accounts on your computer but I get the impression you are past that stage.

So...

If your Messages > Preferences > Accounts > iMessages has more than two emails and those others are used by your kids fro their iMessages  then they will see your iMessages.

Mine contains just the Original Apple ID email and the iPhone Number.

This is an older pic when the @me.com ID was listed as well.

IF you wanted to in some way monitor their activities then Parental Controls is the way to go.

7:51 pm      Friday; April 1, 2016

for the    Points

8:54 pm      Saturday; April 2, 2016